Cartridge case for 20 mm. gun system



y 1963 F- w. LITTLEFORD 3,089,420

CARTRIDGE CASE FOR 20 MM. GUN SYSTEM Filed Jan. 5, 1961 X i J o O 6 O 0". O .o O I "J o 'O O 0 0 0- 0 Q9: [0, o H H 00 .0 0

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Frankw LiPt1anrcf BY 5 2 m United States Patent Army Filed Jan. 5, 1961, Ser. No. 80,959 1 Claim. (Cl. 10243) (Granted under Title 35, U.S. Code (1952), see. 266) The invention described herein may be manufactured and used by or for the Government for governmental purposes without the payment to me of any royalty thereon.

This invention relates to a cartridge case for cartridge used in automatic guns and more particularly to a case tor a cartridge used in 20 mm. guns in which the shoulder of the case is disposed substantially near the head thereof and the said cartridge case has a separate perforated throttling disc therein.

Cartridges of this type are for express use in guns of the type wherein the firing chamber is confined to a shorter length to permit a barrel of considerably less diameter than is usual in order to conserve material and to afford less weight, an especially desirable feature in aircraft ordnance.

In cartridge cases for use with this type of gun, the propellant chamber is located as near to the cartridge head as is feasible and the chamber is confined within the thickest portion of the gun barrel which is the breech end. A perforated wall reduces the pressure from the propellant charge before it enters the forward portion of the cartridge containing the projectile, which is the portion having the least diameter and extends into the barrel of the gun having the least diameter, thus preventing damage to the thinner barrel due to high pressure.

Heretofore, there have been many and varied types of cases, cartridges, the variation generally being in the configuration of the case without any fundamental change in the functional aspects of the case or cartridge. However, most of these cases or cartridges previously designed, while functional in the conventional type of weapon have functional defects when fired in the 20 mm. guns presently being developed and in use by the armed services.

The present invention has been designed to overcome the aforementioned defects by positioning the case shoulder nearer to the case head and incorporating an independent throttling disc which is perforated to permit blast gases to pass from the propellant chamber into the outer bore of the case to reduce the pressure generated by the blast of the propellant.

-A primary object of the invention is to provid a cartridge case in which the shoulder is disposed substantially nearer to the case head than is customary in order to permit reduction of the external diameter of a gun barrel, in which it is fired, nearer its breech end.

Another object is to provide a cartridge for firing in a 20 mm. gun, the cartridge being fabricated with fewer arts. p A further object is to provide a cartridge for firing in a 20 mm. gun in which a separate perforated disc is inserted for proper function of the gun to reduce the chamber pressure from one side of the propellant chamber to the other.

A still further object is to provide a cartridge case for a cartridge providing greater economy in that parts are quickly replaceable and the structure thereof permits of mass production in that the cartridge case is of one piece and the additional components are assembled within its base.

The specific nature of the invention as well as other objects and advantages thereof, will clearly appear from a description of a preferred embodiment as shown in the accompanying drawings in which:

FIG. 1 is a longitudinal sectional view of a cartridge constructed in accordance with the invention, the bullet being omitted; and,

FIG. 2 is an end view of the throttling disc.

In the drawings, 1 indicates generally, the cartridge case of the invention and includes a cylindrical one piece tapering body 2 which tapers more sharply as at 3 towards the cartridge head to form a thickened shoulder portion 4.

Case 7 has an axial bore 5 to receive a bullet (not shown) and is counterbored as at 6 to form a propellant receiving chamber, a propellant 7 being shown in chamher 6 in FIG. 1 by way of illustration.

Bore 6 is internally threaded as at 8 at the rearward or head receiving portion of the cartridge and is adapted to receive a head 9 which has a reduced externally threaded portion 10. Head 9 is provided with the usual primer pocket 11 for receiving the usual primer charge 12.

A throttling disc 13 is shown in assembled position in FIG. 1 and is normally disposed in chamber 6 forwardly of propellant charge 7. This disc is a component of the system of a 20 mm. type gun and is critical as to its func tioning. Disc 13 is provided with perforations 14, best seen in FIG. 2 and serves to reduce the pressure of the blast gases from chamber 6 to bore 5.

Due to the extremely simple construction, assembly of the cartridge is easy. The disc 13 is placed in the forward end of chamber 6, propellant 7 is inserted and then the head 9 is screwed into the threaded end.

It is apparent from the foregoing that the cartridge of the invention will be greatly superior to the previous types of cartridges in that it eliminates the number of threaded parts and by providing a separate disc, greater accuracy has been achieved in positioning the head to datum length, and also improvement results from the external concentricity of the cartridge since the case is made of one symmetrical piece.

Variations and modifications may be effected without departing from the scope of the novel concept of the present invention.

What is claimed is:

In a cartridge case for use in a gun system the combination comprising, a one piece circular in cross section body, said body having a forwardly tapering forward portion and a rear-Ward portion having a cylindrical end part of greater thickness than any portion of said forward portion, said rearward portion further being tapered from said thickened cylindrical part to integrally connect the thickest portion of said forward portion, said rearward portion being of substantially less length than said forward portion, there being a cylindrical axial bore in said forward portion and a coaxial counterbore of greater diameter than said axial bore in said rearward portion con meeting said axial bore, said coaxial bore being internally threaded along a part of its length, an externally threaded head having a generally cylindrical threaded portion and 3 a flange portion of greater diameter than said rearward References Cited in the file of this patent cylindrical portion and said threaded cylindrical portion, UNITED STATES PATENTS said head being secured in said threaded coaxial bore by said threaded cylindrical portion, said counterbore fon'n- 1,355,422 Pedefsen 12, 1920 ing a propellant chamber therein, and a throttling means 5 2,926,607 Muller et 1960 in said propellant chamber, said throttling means includ- 2,985,104 FOX y 1961 ing a separate perforated disc disposed in the forward end FOREIGN PATENTS of said propellant chamber, said disc having a thickness less than the length of and a diameter substantially the 484346 Great Bntam May 1938 same as said propellant chamber. 10 

